1. Which of the following is true about Step-growth polymerisation?a) radical, coordination, anionic, or cationic polymerization, depending on the type of initiationb) polymerization that is catalysed by transition metal salts and complexesc) monomers react by eliminating small molecules like H2O, NH3, CH2O and NaCl in a repetitive manner, Indefinite growth of the polymer occurs at both endsd) monomers react to form first dimers, then trimmers, longer oligomers and eventually long chain polymersView Answer

Answer: dExplanation: Step-growth polymerization refers to a type of polymerization mechanism in which bi-functional or multifunctional monomers react to form first dimers, then trimmers, longer oligomers and eventually long chain polymer.

2. Which of the following is not true about step growth polymerisation?a) Molar mass of backbone chain increases rapidly at early stage and remains approximately the same throughout the polymerizationb) Similar steps repeated throughout reaction processc) Initiator are required for the step growth polymerisationd) Rapid loss of monomer early in the reactionView Answer

Answer: cExplanation: Initiator is not required for the step growth polymerisation. Step-Growth polymerization occurs by consecutive reactions in which the degree of polymerization and average molecular weight of the polymer increase as the reaction proceeds.

3. Which of the following is polymer formed by step-growth polymerization is not classified under condensation polymerisation?a) Polyesterb) Polyurethanec) Polysiloxaned) PolyamideView Answer

Answer: bExplanation: Most step-growth polymers are classified as condensation polymers, but not all step-growth polymers. Polyurethanes formed from isocyanate and alcohol bifunctional monomers) release condensates; in this case, we talk about addition polymers.

4. Which monomers are required for the formation of Bakelite via a typical step-growth polymerization?a) phenol and formaldehydeb) isocyanate and alcoholc) diamine and formaldehyded) ester and phenolView Answer

Answer: aExplanation: The synthesis of first truly synthetic polymeric material, Bakelite, was announced by Leo Baekeland in 1907, through a typical step-growth polymerization fashion of phenol and formaldehyde.

5. Formation of polytriazole polymers via step-growth polymerization is produced from which of the following monomers?a) Compound which bears both alkyne and azide functional groupb) Compound which bears both alkene and azide functional groupc) Compound which bears both alkane and azide functional groupd) Compound which bears both vinyl and azide functional groupView Answer

Answer: aExplanation: Poly-Triazole polymers are produced from monomers which bear both an alkyne and azide functional group. The monomer units are linked to each other by the a 1,2,3-triazole group; which is produced by the 1,3-Dipolar cycloaddition, also called the Azide-alkyne Huisgen cycloaddition.

Answer: aExplanation: The kinetics of the step-growth polymerization can be described with Flory’s equal reactivity principle. If the polymerization is carried out in the presence of a strong acid (sulfonic acids) and if the catalyst concentration is kept constant throughout the process the average degree of polymerization increases linearly with the reaction time, which is a much more favorable situation for obtaining high average molecular weight polymers than the weak-acid catalyzed third-order reaction.

7. What is the trend in the molecular weight of step growth polymer at lower conversion and higher conversion respectively?a) Increase then decreaseb) Decreases an increasesc) Remains samed) Can’t say about molecular weightView Answer

Answer: bExplanation: Step-growth polymers increase in molecular weight at a very slow rate at lower conversions and reach moderately high molecular weights only at very high conversion (i.e., >95%).